Electrochemical oxidation of glucose has been studied for the potential applications as a detector for dissolved glucose in blood or other media. Current commercial blood glucose sensors use an enzyme electrode to oxidize glucose, which is followed with an indirect electrochemical detection of the enzymatic reaction products. Enzyme is relatively expensive, with a limited shelf-life, a low tolerance to elevated temperature, and it is not suitable for industrial applications. Glucose oxidase and glucose hydrogenase were the common enzymes to be immobilized in electrodes and to have selective reactions with glucose in a solution. Inorganic catalyst materials have the advantages of direct electrochemical oxidation, a longer shelf-life, and are resistant to the high temperatures and other harsh operating conditions found in a bioreactor or other industrial applications. The previous investigated materials of inorganic electrocatalysts include platinum, gold, ruthenium, iridium, their mixtures, and their oxides. A high oxidation potential was required to oxidize glucose and the current density was low, thus unfavorable for practical devices of glucose oxidation.
Although the theoretical concept of using glucose to power a bio-fuel cell has been mentioned in the past, a workable glucose-air fuel cell has not been demonstrated due to poor performance of the previously tested catalysts which include enzymes. The previous power densities reported were in the orders of microwatts per square centimeters. Glucose is inexpensive, safe, commonly available, conveniently stored, non-toxic, and hazard free. It offers certain advantages over the common fuels considered for portable fuel cells, such as hydrogen, methanol, and borohydride.
In U.S. Pat. No. 5,660,940, a biofuel-powered fuel cell is described with glucose, arabinose, and other carbohydrates as possible fuels. The fuel cell operates at above 90 ° C. with a two-step oxidation process using platinum, ruthenium, and vanadium as catalysts. In U.S. Pat. No. 5,976,719, a biofuel cell is described with glucose as a possible fuel. The oxidation is indirect and requires a microorganism to react with the glucose to generate other species to power the fuel cell. In U.S. Pat. No. 4,294,891, an implantable bio-oxidant fuel cell is described using glucose as a fuel and platinum, ruthenium, rubidium, iridium, nickel as catalysts for the anode. The power generated was in microwatts range. In U.S. Pat. No. 4,447,506, a ternary fuel cell catalyst containing platinum, cobalt, and chromium was disclosed for use as cathode material for oxygen reduction in acid medium, but not to be used as an anode.